If the sun suddenly became a black hole, would the earth be sucked in?

A picture of a real black hole, taken by the Event Horizon Telescope collaboration

According to a widespread belief, black holes suck, inexorably, any object within the range of their gravitational force, regardless of the kinematic state of the poor prey. In fact, this is misconception. A black hole’s gravitational field is no different from the one of any other body. …


Thank you for your interesting considerations (as usual). It took some time to me to respond because in this period I am very busy with teaching.

I mostly agree with what you say about the equivalence sign "=". On the other hand, I must admit that in certain cases (like…


Using Arduino, it is straightforward to investigate the Faraday-Neumann-Lenz Law

The pandemic has severely restricted the possibilities to attend practicals at schools and university. Arduino can be exploited, not only to mitigate the effects of the lockdowns, but to introduce a new way of engaging students in laboratory activities. …


Teaching energy before forces is not only possible but desirable.

This post was motivated by a tweet by Frank Noschese, reproduced below, to which I responded that I am a big fan of the “energy first” approach.

I must say that the approach I am advocating is not an idea of myself. I started thinking about it after reading a…


Using Arduino we can measure temperature and pressure of a gas and study its equation of state

In my last post, I show how to obtain experimental data from Arduino via BLE. As promised, I now come to the collection and the interpretation of these data, in the case of an experiment in which a gas is subject to an isovolumetric process, i.e., …


How to collect and publish data using Bluetooth Low Energy with Arduino

In this post, I illustrate operation of an Arduino with BLE (Bluetooth Low Energy). As usual, physics being my field, I do not discuss a generic example (the equivalent of “Hello, World!”), but a concrete physics application. Sometimes, for brevity or clarity, I will not be rigorous, and purists may…


General relativity is one of the most technically difficult physics theories, as it requires uncommon knowledge and mathematical skills. However, it is possible to calculate the relativistic effects induced by the curvature of space-time with good precision, and even to derive its formula, with a few simple arguments.

We know…


Almost like a flush toilet, indeed…

Transistors are the building blocks of our electronic gadgets: from smartphones to computers, toys, cooking devices, cleaning tools, etc.

Despite their ubiquity, only a few people know about how they work. In fact, understanding their principles of operation is not so hard.

The diode: a transistor building block

In order to understand how a transistor work…


So, how does it melt the ice?

Deicing roads requires spreading salts over them. Photo by Simon English on Unsplash

In a previous post of mine, I illustrated a brief history of temperature scales in which I recalled that the reason for which 0 °F corresponds to -18 °C is that the latter was the lowest temperature that Daniel Gabriel Fahrenheit could achieve in his laboratory.

Such a temperature can…


The most widely adopted temperature scale is the Celsius or centigrade scale. Nowadays, we use these terms as synonyms, but, in fact, they were not such, originally. …

Giovanni Organtini

Professor of Physics at Sapienza Università di Roma. Member of the CMS and PADME collaborations. Arduino advocate and phyphox ambassador.

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